1. Field of the Invention
This invention relates to catalyzed processes for the reaction of olefin and oxygen in a water or water-carboxylic acid reaction medium to provide the corresponding glycol and glycol ester.
2. Description of the Prior Art
It is known in the art to react an olefin with water and oxygen in the liquid phase in the presence of molecular iodine as catalyst to provide glycol. Illustrated for ethylene, the reaction may be represented as follows: ##EQU1## This process is described in U.S. Pat. No. 1,982,545 to Skarblom which, in addition to molecular iodine, discloses other iodine-containing catalysts which provide elemental iodine under the conditions of the reaction, i.e., hydrogen iodide, ethylene iodide, potassium triiodide, ferric iodide and glycol iodinehydrine. According to U.S. Pat. No. 3,928,474 to Witheford, the co-production of excessive quantities of high boiling components such as diethylene glycol and triethylene glycol which results from the Skarblom process can be prevented by carrying out the above reaction at elevated temperature and superatmospheric pressure and thereafter recovering the product ethylene glycol by distillation carried out at subatmospheric pressure.
U.S. Pat. No. 4,088,286 to Hirose et al. describes a process for obtaining glycols from olefins of 2 to 4 carbon atoms in which the olefin is reacted with oxygen and water in the liquid phase at 100.degree.-200.degree. C. employing a catalyst containing copper and/or iron cations and an anion which at least includes a bromine ion which can solubilize copper and/or iron. The catalyst can be a copper bromide or an iron bromide itself or some other copper or iron compound together with a suitable source of solubilizing bromine anion, e.g., molecular bromine, hydrogen bromide or an organobromide. With limited exception, patentees strongly warn against conducting the reaction in the presence of molecular bromine or free hydrobromic acid as these species are said to be useless, even detrimental, to the process.
In a related process for obtaining glycol and/or glycol ester, olefin is reacted with oxygen and carboxylic acid, optionally in the presence of added water, employing any one of a variety of catalysts. The reaction, commonly referred to as oxyacylation, is usually carried out in the liquid phase at elevated temperature and superatmospheric pressure. Thus for the reaction of ethylene, oxygen and acetic acid to produce ethylene glycol diacetate, the overall chemical reaction can be considered to proceed in accordance with the reaction: ##EQU2##
In addition to diester, this reaction will also result in the production of some monoester. Depending in large measure upon the catalyst employed, reactions other than the aforesaid oxyacylation reaction can take place, and to the extent they reduce product yield, complicate recovery and separation techniques and increase raw material and production costs, they are undesirable. It is, of course, recognized that simultaneous reaction of two different carboxylic acids will result in a mixture of products containing symmetrical diesters and unsymmetrical (mixed) diester. The alkylene glycol mono- and diesters are readily hydrolyzed to the glycols and to the carboxylic acid(s) employed in their production employing known and conventional techniques, e.g., hydrolysis and saponification with alkali followed by acid treatment.
Numerous proposals for oxyacylation catalysts have been made. U.S. Pat. No. 2,519,754 employs as catalyst, a hydrohalide such as hydrobromic acid or an organic acid capable of generating the free acid such as an aliphatic bromide. Snyder's process described in U.S. Pat. No. 2,701,813 employs certain metals or metal compounds such as silver, compounds of metals of the first transition group of the periodic system, particularly their salts, and salts of such heavy metals which are capable of existing in more than one oxidation state such as the acetates, stearates and naphthenates of cobalt, manganese, copper and the like. The olefin oxidation process of U.S. Pat. No. 3,427,348 to Olson employs selenium dioxide in admixture with a mineral acid such as hydrochloric acid. U.S. Pat. Nos. 3,479,395 and 3,637,515 to Huguet each describes a process employing tellurium dioxide solubilized with a halide salt. Lutz, in U.S. Pat. No. 3,542,857, employs a cerium (III) or cerium (IV) salt which is soluble in the carboxylic acid component of the oxyacylation reaction medium. U.S. Pat. Nos. 3,668,239 and 3,789,065 to Kollar, and U.S. Pat. No. 3,907,874 to Harvey et al. each employ a source of metal cation such as that of tellurium and a source of bromine. U.S. Pat. Nos. 3,689,535 and 3,985,795 to Kollar and U.S. Pat. No. 3,872,164 to Schmidt each describe a process for preparing ethylene glycol esters by contacting ethylene, bromine or chlorine, or compound of bromine or chlorine, and oxygen in the presence of a carboxylic acid and a variable metal cation such as antimony cation. Similarly, the Valbert (U.S. Pat. No. 3,715,388) and Hoch (U.S. Pat. No. 3,715,389) catalysts include bromine or a bromine compound and a source of metal cation such as arsenic or antimony cation. U.S. Pat. No. 3,770,813 to Kollar describes the use of a catalyst containing iodine or iodide anion and a heavy metal cation of atomic number 21-30 and 48. U.S. Pat. No. 3,778,468 employs a catalyst containing selenium cation and chlorine, bromine or a compound thereof. Gaenzler et al. U.S. Pat. No. 3,916,011 describe an oxyacylation catalyst which is a complex formed between a compound of titanium and a compound of lithium, beryllium, magnesium, calcium, boron, aluminum, silicon or phosphorus, or a complex formed between compounds of at least two of the elements boron, aluminum, silicon and phosphorus. The oxyacylation catalyst of Gaenzler et al. U.S. Pat. No. 3,981,908 contains a compound of boron, aluminum, silicon, phosphorus or a combination thereof, and a compound of iron, copper or a combination thereof. The Schmerling (U.S. Pat. No. 4,009,203) catalyst is the reaction product of a tin halide and a carboxylic acid.
Each of the aforesaid catalysts is subject to one or more disadvantages, either in regard to the complexity of the apparatus required to carry out the process and/or in regard to the degree of selectivity of the reaction of olefin, oxygen and carboxylic acid for alkylene glycol ester.